FI66195B - FOERFARANDE FOER NEDSAETTNING AV KCENTRATION AV EN FOERORENING - Google Patents

Description

661 95

METHOD FOR REDUCING THE CONCENTRATION OF THE POLLUTANT -FÖRFARANDE FÖR NEDSÄTTNING AV KONCENTRATION AV EN FÖRORENING

The present invention relates to the purification of organic compounds and in particular to methods for reducing the concentration of relatively dark impurities in a composition of matter comprising at least one desired compound and one or more such impurities.

In particular, the invention relates to a process for reducing the concentration of an impurity which belongs to a composition comprising a impurity and a mixture of saturated and / or unsaturated aliphatic carboxylic acids having 8 to 24 carbon atoms, the impurity being darker in color than the desired product.

It is often desirable to improve, i.e. brightens the color of organic compounds intended for various industrial purposes. It is known that treatment of many organic compounds or compositions with sodium hydride can cause color improvement of the compounds or compositions. However, it has previously been assumed that treatment with sodium borohydride must be carried out in the system at an alkaline, or at least neutral, pH-ar-20.

This belief that the use of sodium borohydride to eliminate dark colored impurities can only be realized at neutral or alkaline pH is not unbelievable in particular because at acidic pH 25 borohydride decomposes to form hydrogen.

Illustrating the treatment with sodium borohydride, the compound to be purified being a carboxylic acid, treatment with sodium borohydride would have resulted in the conversion of the acid to the corresponding salt in aqueous solution and subsequent acidification and separation of the acid from the aqueous solution.

This separation operation can be difficult because often emulsions, either water-fat or fat-water emulsions, are well formed and these emulsions must be "broken" before separation of 266,195 acids can be performed. The separated acid must then be dried and distilled. It is at this final stage of distillation that color improvement is usually observed. It has been assumed that the colored impurities are carbon-5 carbonyl compounds or their derivatives, and that sodium borohydride converts these impurities into products that do not distill off with carboxylic acids.

According to the present invention, there is provided a method of reducing the concentration of an impurity in a composition comprising a mixture of an impurity and saturated and / or unsaturated aliphatic carboxylic acids having from 8 to 24 carbon atoms, the impurity being darker in color than the desired product. In the process according to the invention, the substance combination and the boro-15 hydride are brought together at an acidic pH and the resulting mixture is distilled.

Thus, it has now been found that, contrary to all previous practice, treatment with borohydride can be carried out at an acidic pH. As can be seen from the above, the benefits of this 20 are substantial. Upon purification of the carboxylic acid, the borohydride can be added to the acid in the absence of water, and the resulting mixture can be distilled to directly produce the purified final product.

The borohydride is preferably sodium borohydride.

25 Fatty acids of the composition to be cleaned, i.

saturated and / or unsaturated aliphatic carboxylic acids preferably contain 14 to 20, most preferably 16 to 18 carbon atoms. A particularly preferred acid is an aliphatic carboxylic acid having 18 carbon atoms.

30 Publications Ullmanns Encyklopädie der Technischen

Chemie, 3rd Edition, Volume 7, 1956, pp. 504-505 and U.S. Pat.

Unlike the present method, the known methods of 3,471,536 are based on the alkaline treatment of fatty acids and, conversely, the treatment of fatty acids with an amino compound for the purification of carboxylic acids. In said publications, borohydride has not been used to reduce the concentration of an impurity and / or to remove an impurity at an acidic pH.

Again, using an example, a composition of matter known as tall oil is obtained as a waste product by cooking wood 5 into cellulose in papermaking. Tall oil contains a mixture of fatty acids, these acids being mainly unsaturated carboxylic acids with a number of carbon atoms of 14 to 24, mainly 16 to 18, and the main fraction being a fatty acid or acids containing 18 to 10 carbon atoms.

The crude tall oil is a dark colored composition and is distilled to give a crude fatty acid mixture that is brown in color. Such a mixture of fatty acids has a number of uses, e.g. in the manufacture of varnishes in connection with it for paints or surface treatments, for printing inks and for the manufacture of soap and detergents. Especially for paints, finishes and light color inks, there is a need to reduce the darkness of the fatty acid mixture. Prior to the present invention, treatment with sodium borohydride would have resulted in the complex procedure of saponification mentioned above, treatment with sodium borohydride and subsequent separation of fatty acids by re-acidification, drying and finally distillation. The present invention makes it possible to form a fatty acid mixture having the desired light color by directly treating the mixture with sodium borohydride, the mixture being distilled simultaneously or immediately thereafter.

The amount of sodium borohydride used depends on the amount of impurities that react with the sodium borohydride present.

These impurities may include not only dark impurities but also light impurities which may also be reactive with sodium borohydride. The amount of sodium borohydride used depends on its rate of decomposition under the treatment conditions. The amount of sodium borohydride 35 used in practice is normally ascertained after suitable experiments 4 66195 have been carried out to obtain a product having the desired light color. However, it has been found that only small amounts of sodium borohydride are required to significantly reduce the color of compositions such as the above-mentioned crude tall oil and the mixture derived from tall oil. The preferred amount of sodium borohydride is 0.01-0.5 wt% (based on the weight of the fatty acid mixture). Most preferably, the amount of sodium borohydride is 0.02 to 0.05% by weight. It has been found that the optimum amount of sodium borohydride is about 0.03% for a crude fatty acid mixture from tall oil. The color of the product 10 thus obtained progressively becomes lighter as the concentration of sodium borohydride increases to this optimum value. Above this amount, a substantial improvement is no longer usually observed.

It has been found that the product obtained according to the process of the present invention not only has a lighter color than the composition before treatment, but also a good increase in color stability in the product and at least comparable to products obtained by treating sodium borohydride with alkaline pH.

After mixing the sodium borohydride with the mixture to be treated, the mixture can be heated before distillation.

For example, the mixture can be heated at 50-80 ° C for about 1-3 hours at normal atmospheric pressure. It has been found that at temperatures above about 80 ° C the evolution of hydrogen becomes essential when treating a crude fatty acid mixture obtained from tall oil.

The distillation can be carried out immediately after the above-mentioned heat treatment or, alternatively, it can be carried out for some time, e.g. many days after the heat treatment, without decomposing the final product.

Typically, the crude fatty acid mixture from tall oil is heated at about 70 ° C for about one hour and the resulting mixture is then distilled. However, the temperature and duration of this heating step prior to distillation can be varied over a wider range and it is likely to be more important to ensure close mixing of the sodium borohydride with the composition to be treated prior to the distillation step. It has been assumed that no less satisfactory results can be obtained by omitting the heating step before distillation when such close mixing is achieved.

5 As regards the distillation itself, this is vacuum distillation in the case where the composition is a crude fatty acid mixture obtained from tall oil.

The addition of sodium borohydride can be made directly to the reaction vessel as a powder or concentrated slurry for the composition to be treated. Preferably, the air ejector is adapted to disperse the hydrogen formed in the reaction vessel. The capacity of the air ejector used depends on the amount of sodium borohydride to be added as well as the temperature of the material assembly to be treated. The method of the present invention can be carried out either continuously or as a batch process. It has been found that sodium borohydride selectively reduces color-forming impurities without affecting the yield or the properties of the fatty acid mixture, respectively, when the mixture is derived from tall oil. A small amount of sodium metaborate is formed as a by-product, which remains after distillation.

Embodiments of the present invention will be illustrated by way of examples. In the following examples, the color stability of the fatty acid mixture was determined by heating 20 g of samples in a 20 mm diameter glass tube by placing the tube in an oven maintained at 200 ° C for 1 hour. Color measurements were performed using a Cardner 1963 scale.

Example 1 (a) For comparison, 1200 parts by weight of a crude fatty acid mixture (obtained from tall oil) was heated to 30-70 ° C, kept at this temperature for 1 hour without further additives and then distilled in vacuo. A small number of precursors and the main fraction were recovered.

(b) 1200 parts of the same crude fatty acid mixture as in (a) 35 were heated to 70 ° C. 0.03% sodium borohydride powder was mixed here and allowed to react at temperature for one hour. Vacuum distillation was then performed in the same manner as in (a).

, f 5 Foreword Main verse Residue 'I' (a) (bj ~ (a) (b) j (a) (b) j I i p-% 5.3 5.8 85.1 84.8 j 9.6 9.4; 10 Acid value - - 187.0 187.0 j159. 3 120.0 '% / fatty acid - - 89.1 88.4, 76.9 73.8 i% / resin acid - - 5.4 6.2 | 18.8 21.0.

% / Non-Saip. - - 5.3 5.2; 4.1 5.1!

Iodine value -! - 154.2153.1 * - -J

i 15 Gardner color 96 7 5! - | i 'Color fastness - 9 6! -! (1 h / 200 ° C) j «j! _! _I_i 20 Example 2 In this example, the pretreatment was kept in a mini. Sodium borohydride was mixed with the same fatty acid mixture as in Example 1 for 30 min at 20 ° C, at which time it was completely mixed. Vacuum distillation was performed at 25 ° C as in Example 1.

Esijae Pääjae! % Borohydride ~ 0.0l | 0.02 '0.05 Ö 0.01I 0.021 0.05 30 I Ϊ p-% 5.4 5.6 5.4 5.8 87.1 87.4 86.6 | 87.3

Gardner color 9776 7665 Color fastness - - - 9876 (1 h / 200 ° C) 35 ------! - 7 66195

Example 3

A concentrated slurry containing 0.3 parts of sodium borohydride was formed at room temperature in 50 parts of the same fatty acid mixture as in Example 1. This was added to a further 1140 parts of 5 fatty acid mixtures maintained at 60 ° C to give a level of 0.025% sodium borohydride. The mixture was stirred at this temperature for 3 h. Vacuum distillation was performed, this time 3 pre-fractions and 2 main fractions were taken.

10 Foreword Fraction 2 Fraction 3 (a) (b) (a) '(b) (a) (b) p% 5.7 5.8 42.0 42.0 42.6 43.6

Gardner color 97 87 75 15 Color stability • - 86 (1 h / 200 ° C) 20 25 30 35

Claims (12)

A process for reducing the concentration of a contaminant forming a composition comprising said contaminant and a mixture of saturated and / or unsaturated aliphatic carboxylic acids having between 8 and 24 carbon atoms, the contaminant having a darker color than the desired compound, characterized in that in process, said composition is contacted with each other and a borohydride at acidic pH and the resulting mixture is distilled. A process according to claim 1, characterized in that the borohydride is sodium borohydride. Process according to claim 1 or 2, characterized in that the aliphatic acids have between 14 and 20 carbon atoms. Process according to any of the preceding claims, characterized in that the aliphatic acids have between 16 and 18 carbon atoms. Process according to any of the preceding claims, characterized in that the composition comprises an aliphatic carboxylic acid of 18 carbon atoms. Process according to any of the preceding claims, characterized in that the composition is talloija. A process according to any of the preceding claims, characterized in that the borohydride is used in an amount of between 0.01 and 0.5% by weight based on the weight of the composition. Process according to any of the preceding claims, characterized in that the borohydride is used in an amount of between 0.02 and 0.05% by weight based on the weight of the composition. 9. A process according to any of the preceding claims, characterized in that the composition is tailored and the borohydride is sodium borohydride used in an amount of about 0.03% by weight calculated